This application is based on Japanese Patent Application Nos. 2000-357254 filed on Nov. 24, 2000 and 2001-273015 filed on Sep. 10, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a warning apparatus.
2. Discussion of Related Art
JP-A-6-231400 discloses a warning apparatus provided on an automotive vehicle to generate a warning signal or an alarm indication when a distance between the vehicle and an object in front of the vehicle has become shorter than a predetermined threshold value. In this warning apparatus, the threshold value of the distance is determined on the basis of a running speed, a free running time and a maximum deceleration value of the vehicle. The free running time and maximum deceleration value of the vehicle are set or determined for a specific operator or driver of the vehicle, on the basis of empirical data indicative of braking conditions of the vehicle in which the vehicle was braked by the specific operator in the past. Accordingly, the warning apparatus disclosed in the above-identified publication is capable of generating the warning signal at a timing that suits the particular vehicle operating or driving characteristic or habit of the specific operator.
It is therefore an object of the present invention to provide a warning apparatus provided on an automotive vehicle, which generates a warning signal at a timing that better suits a particular vehicle operating characteristic or habit of a specific operator of the vehicle, than the warning apparatus disclosed in the publication identified above.
The above object may be achieved according to any one of the following modes of the present invention in the form of a warning apparatus. Each of the following modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combination thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A warning apparatus for an automotive vehicle, operable to generate a warning signal when a distance between the vehicle and an object existing in front of the vehicle is shorter than a predetermined threshold value, comprising:
a characteristic-value storage portion which stores at least one characteristic-value relationship between at least two of a plurality of brake operating characteristic values relating to a braking operation by an operator of the vehicle to brake the vehicle; and
a threshold-value determining portion operable to determine the threshold value of the distance, on the basis of at least one of an estimated braking state of the vehicle estimated on the basis of the at least one characteristic-value relationship stored in the characteristic-value storage portion; a running-state quantity indicative of a running state of the vehicle; and a moving-state quantity indicative of a moving state of said object.
The warning apparatus according to the above mode (1) is arranged to generate a warning signal or provide a warning indication when the actual distance between the automotive vehicle in question (hereinafter referred to as xe2x80x9cpresent vehiclexe2x80x9d) and the object in front of the present vehicle (e.g., a front vehicle running in front of the present vehicle, or a stationary object) has become smaller than the predetermined threshold value. In the present warning apparatus, the threshold value of the actual distance is determined on the basis of at least one of the estimated braking state of the present vehicle estimated on the at least one characteristic-value relationship between at least two brake operating characteristic values relating to the vehicle operator""s braking operation to brake the present vehicle, the running-state quantity indicative of the running state of the present vehicle, and the moving-state quantity indicative of the moving state of the object. This arrangement permits the warning apparatus to generate the warning signal at a timing that better suits the specific brake operating characteristic or habit of the vehicle operator, than in the known warning apparatus.
Each characteristic-value relationship used is a relationship between two brake operating characteristic values relating to the vehicle operator""s operation to apply a normal brake to the vehicle during normal running of the vehicle or to apply an emergency brake to the vehicle. The at least one characteristic-value relationship is selected depending upon the object of generating the warning signal. Each characteristic-value relationship used by the threshold-value determining portion may be determined either theoretically or experimentally. The case of the theoretical determination may be based on an human-oriented engineering technology. The characteristic-value relationship may be either held constant, or changed depending upon the running state of the present vehicle and the state of the roadway surface on which the present vehicle is running. Further, the characteristic-value relationship may be updated by a learning compensation technique. The at least one characteristic-value relationship may consist of only one relationship between two brake operating characteristic values, or at least two characteristic-value relationships among three or more brake operating characteristic values. In the latter case, the at least two characteristic-value relationships may consist of two or more relationships of one brake operating characteristic value with the other brake operating characteristic values, or two or more relationships of two or more brake operating characteristic values with respective two or more other brake operating characteristic values. Alternatively, two or more characteristic-value relationships are determined by each other in connection with each other, such that one brake operating characteristic value is related to another characteristic value, and a further characteristic value is related to the above-indicated one characteristic value, and so on.
The running-state quantity may include the running speed and/or acceleration value of the present vehicle, and the moving-state quantity of the object may similarly include the moving speed and/or acceleration value of the object. Where the running-state quantity include both of the running speed and acceleration value of the present vehicle while the moving-state quantity include both of the moving speed and acceleration value of the object, it is possible to obtain a relative speed and a relative acceleration value of the present vehicle and the object.
(2) A warning apparatus according to the above mode (1), wherein the characteristic-value storage portion stores at least two characteristic-value relationships of one of the plurality of brake operating characteristic values with respective at least two other characteristic values of the plurality of brake operating characteristic values, and the threshold-value determining portion is operable to estimate at least two braking-state quantities indicative of a braking state of the present vehicle, on the basis of the above-indicated one brake operating characteristic value and the characteristic-value relationships.
In the warning apparatus according to the above mode (2), the characteristic-value storage portion stores at least two characteristic-value relationships of one brake operating characteristic value with the other brake operating characteristic values. Accordingly, at least two braking-state quantities of the present vehicle can be obtained on the basis of the above-indicted one brake operating characteristic value and the at least two characteristic-value relationships.
(3) A warning apparatus according to the above mode (1) or (2), wherein the characteristic-value storage portion stores at least one characteristic-value relationship selected from a plurality of relationships between or among at least two of; (a) an operating-speed quantity relating to a speed of the braking operation by the operator to brake the vehicle; (b) a vehicle-deceleration quantity indicative of a deceleration value relating to the vehicle as a result of the braking operation by the vehicle to brake the vehicle; and (c) a relative-position quantity relating to a relative position between the vehicle and the object upon the braking operation.
In the warning apparatus according to the above mode (3), the characteristic-value storage portion stores at least one of: (i) a relationship between the operating-speed quantity and the vehicle-deceleration quantity; (ii) a relationship between the operating-speed quantity and the relative-position quantity; (iii) a relationship between the vehicle-deceleration quantity and the relative-position quantity; and (iv) a relationship among the operating-speed quantity, the vehicle-deceleration quantity and the relative-position quantity.
For instance, the operating-speed quantity may be a speed value or values relating to an operation of a manually operable brake operating member by the vehicle operator. For example, the operating-speed quantity includes a statistically processed value of one or both of (i) a speed of switching of the vehicle operator from an operation of an accelerator pedal of the vehicle to an operation of the brake operating member (brake pedal), and (ii) a speed of operation of the brake operating member. The operating-speed quantity may include a required time of the operator""s braking operation, and/or a rate of increase of the above-indicated speed of the braking operation. In this respect, it is noted that the required time decreases with an increase of the speed of the operator""s braking operation, and that the rate of increase of the above-indicated speed increases with the increase of the speed of the operator""s braking operation.
As described below, the operating-speed quantity is determined by the vehicle operator, that is, by the mental factors and locomotive capacity of the vehicle operator. For instance, a hasty or prompt vehicle operator tends to perform the braking operation at a higher speed than a gentle or slow vehicle operator, and a vehicle operator who likes to drive a vehicle in a sporty fashion tends to perform the braking operation at a higher speed than a vehicle driver who likes to drive a vehicle in a steady fashion. Further, the upper limit of the speed of the braking operation may be determined by the locomotive capacity of the vehicle operator. In addition, the speed of the braking operation of the same operator tends to be higher when the operator is relatively strained or tense than when the operator is not relatively relaxed. Thus, the operating-speed quantity consists of at lest one value suitable for accurate evaluation of the mental states or factors and locomotive capacity of the specific vehicle operator.
The vehicle-deceleration quantity includes not only a deceleration value of the present vehicle per se, but also amounts of operation of the brake operating member by the vehicle operator, such as the operating force and stroke, a braking force produced as a result of the operator""s operation of the brake operating member, and a ratio of utilization of the friction force between the vehicle wheels and the roadway surface. For instance, the ratio of utilization of the friction force may be represented by a ratio of the actual deceleration value of the present vehicle to a maximum deceleration value which is determined by the friction coefficient of the roadway surface. While the actual deceleration value of the vehicle is lower than the maximum deceleration value, the actual deceleration value increases with an increase of the amount of operation of the brake operating member, and therefore the ratio of utilization of the friction force increases with the increase of the amount of operation of the brake operating member. When the friction coefficient of the roadway surface is relatively low, the maximum deceleration value is relatively low. In this case, the vehicle operator generally adjusts the operating amount of the brake operating member so that the actual deceleration value does not exceed the relatively low maximum deceleration value. Accordingly, the actual deceleration value of the vehicle increases with an increase of the operating amount of the brake operating member. When the friction coefficient of the roadway surface is relatively low, the ratio of utilization of the friction force is generally higher than when the friction coefficient is relatively high. However, the actual deceleration value and the ratio of utilization of the friction force increase as the operating amount of the brake operating member is increased. In this respect, the ratio of utilization of the friction force can be used as the vehicle-deceleration quantity. The actual deceleration value of the present vehicle for a given value of the friction coefficient of the roadway surface can be obtained on the basis of the ratio of utilization of the friction force. However, the actual deceleration values for different values of the friction coefficient of the roadway surface cannot be obtained on the basis of only the ratio of utilization of the friction force. Where the ratio of utilization of the friction force and the friction coefficient of the roadway surface are both known, the actual deceleration value of the vehicle can be obtained. Therefore, the ratio of utilization of the friction force and the friction coefficient of the roadway surface may preferably be used as the vehicle-deceleration quantity.
The relative-position quantity may include a distance between the distance between the present vehicle and the object in front of the present vehicle, and a state of change of this distance. The distance between the vehicle and the front object may be an absolute distance, or a distance as felt by the vehicle operator. Even when the actual distance between the present vehicle and the object is constant, the distance as felt by the vehicle operator is shorter than the actual distance, where the relative speed between the vehicle and the object (the speed at which the present vehicle is approaching the object) or the running speed of the present vehicle is relatively high. The distance as felt by the vehicle operator may be obtained by dividing the distance between the vehicle and the object, by the running speed of the vehicle or the speed at which the vehicle is approaching the object. The state of change of the distance may include the relative speed of the vehicle and the front object, and the relative acceleration value (a rate at which the vehicle and the object are moving toward or away from each other).
Between the operating-speed quantity and the vehicle-deceleration value, there is a relationship or tendency that a vehicle operator having a relatively high speed of the braking operation has a relatively high deceleration value of the vehicle, while a vehicle operator having a relatively low speed of the braking speed has a relatively low deceleration value of the vehicle. Between the operating-speed quantity and the relative-position quantity, on the other hand, there is a relationship or tendency that the vehicle operator having a relatively high speed of the braking operation has a relatively short distance between the present vehicle and the front object, while the vehicle operator having a relatively low speed of the braking operation has a relatively long distance between the vehicle and the object. These relationships or tendencies were confirmed by experiments. Accordingly, the determination of the threshold value of the distance on the basis of these tendencies permits the warning apparatus to generate a warning signal at a timing that best suits the specific brake operating characteristic or habit of the particular operator of the vehicle.
(4) A warning apparatus according to any one of the above modes (1)-(3), wherein the characteristic-value storage portion stores at least one characteristic-value relationship selected from a plurality of relationships between or among at least two of: (a) a desired-safety-margin quantity relating to a safety margin desired by the operator in connection with the braking operation by the operator to brake the vehicle, (b) a required-vehicle-deceleration quantity relating to a required deceleration value of the vehicle as felt by the operator upon the braking operation, and (c) a critical-relative-position quantity relating to a relative position between the vehicle and the object at which the operator feels it necessary to initiate the braking operation.
The desired safety margin relates to a degree of necessity of the braking operation as felt by the vehicle operator. The desired safety margin is relatively large when the degree of necessity of the braking operation as felt by the operator is relatively low during a normal running of the vehicle. The desired safety margin is a degree of the safety margin desired or preferred by the vehicle operator in connection with the braking operation. For instance, a gentle or slow vehicle operator tends to desire a higher degree of safety margin in the braking operation than a hasty or prompt vehicle operator, while a vehicle operator who likes to drive the vehicle in a steady fashion tends to desire a higher degree of safety margin in the braking operation than a vehicle operator who likes to drive the vehicle in a sporty fashion. The same vehicle operator has a higher degree of safety margin when the operator is relatively strained than when the operator is relatively relaxed. The desired safety margin is determined primarily by the operating characteristic or habit and the metal states of the vehicle operator. The vehicle operator whose desired safety margin is relatively large generally initiates the braking operation at a relatively early point of time, than the vehicle operator whose desired safety margin is relatively small.
The vehicle operator whose desired safety margin is relatively large usually operates the brake operating member at a relatively low speed, than the vehicle operator whose desired safety margin is relatively small. In this sense, the desired safety margin per se is a subjective value as felt by the vehicle operator, and can be adjusted into an objective value on the basis of the operating-speed quantity described above with respect to the above mode (3). Accordingly, the desired-safety-margin quantity is suitable to estimate the required braking distance of the vehicle during a normal running of the vehicle, and suitable to determine the threshold value of the distance between the vehicle and the object which is used to determine whether the warning signal is generated or not, during the normal running of the vehicle.
The deceleration value of the vehicle as a result of the braking operation by the vehicle operator is usually determined by the metal state of the vehicle operator. For instance, the vehicle operator whose desired safety margin is relatively large tends to perform the braking operation that results in a lower value of deceleration of the vehicle, than the vehicle whose desired safety margin is relatively small.
The critical-relative-position quantity relating to the relative position between the vehicle and the object at which the vehicle operator feels it necessary to initiate the braking operation is usually determined by the metal state of the vehicle operator. For instance, the vehicle operator whose desired safety margin is relatively large tends to feel it necessary to initiate the braking operation when the distance between the vehicle and the object is larger, than the vehicle operator whose desired safety margin is relatively small.
(5) A warning apparatus according to any one of the above modes (1)-(5), wherein the characteristic-value storage portion stores at least one characteristic-value relationship selected from a plurality of relationships between or among at least two of: (a) a promptness quantity relating to promptness of the operator to perform the braking operation; (b) an operating-force quantity relating to an operating force to be produced by the operator to perform the braking operation; and (c) a critical-relative-position quantity relating to a relative position between the vehicle and the object at which the operator feels it necessary to initiate the braking operation.
The promptness quantity is a quantity indicative of one of the locomotive capacity values of the vehicle operator which relates to the promptness to perform the braking operation. A vehicle operator having a relatively high degree of locomotive capacity, for instance, a vehicle operator having a relatively high athletic response is capable of performing the braking operation at a relatively high speed. In this sense, the promptness may be represented by the operating-speed quantity described above with respect to the above mode (3) of this invention. Since the upper limit of the speed of the braking operation by the operator is determined by the locomotive capacity of the operator, the operator is not able to operate the brake operating member at a speed higher than a value corresponding to the locomotive capacity of the operator. For example, a time duration from a moment at which the operator feels it necessary to initiate the braking operation to a moment at which the braking operation is actually initiated is a quantity accurately representative of the brake operating promptness of the operator. This time duration is generally referred to as xe2x80x9cfree running timexe2x80x9d of the vehicle. The lower limit or minimum value of this free running time may be suitably used to determine the threshold value of the distance between the vehicle and the front object, which is used to determine whether the warning signal should be generated or not.
The operating-force quantity includes: an operating force and an operating stroke of the brake operating member operated by the vehicle operator; a braking force produced as a result of the braking operation by the vehicle operator; a deceleration value of the vehicle established as a result of the braking operation; a ratio of utilization of the friction force between the vehicle wheels and the roadway surface; and the friction coefficient of the roadway surface. The operating-force quantity is also generally determined by the locomotive capacity of the operator. The vehicle operator having a relatively high degree of locomotive capacity (and usually a relatively high level of promptness) tends to operate the brake operating member with a relatively large operating force. Since the vehicle operator tends to control the operating force of the brake operating member so as to establish a deceleration value of the vehicle which the vehicle operator feels necessary, the operating-force quantity may be represented by the required-vehicle-deceleration quantity described above with respect to the above mode (4).
The critical-relative-position quantity as felt by the vehicle operator is also generally determined by the locomotive capacity of the operator, in particular, by the promptness. The vehicle operator having a relatively high degree of locomotive capacity has a relatively long critical distance between the vehicle and the front object, at which the operator feels it necessary to initiate the braking operation.
(6) A warning apparatus according to any one of the above modes (1)-(5), wherein the characteristic-value storage portion stores at least one of:
(a) a relationship between a braking-delay time between a moment at which the operator feels it necessary to initiate the braking operation and a moment at which the braking operation is actually initiated, and a deceleration value of the vehicle to be established by the braking operation; and
(b) a relationship between the braking-delay time and a relative-position quantity relating to a relative position between the vehicle and the object.
In the warning apparatus according to the above mode (6), the characteristic-value storage portion stores at least one of the two characteristic-value relationships (a) and (b) indicated above.
The braking-delay time is a time duration between the moment at which the vehicle operator feels it necessary to initiate the braking operation and the moment of the actual initiation of the braking operation. The moment at which the vehicle operator feels it necessary to initiate the braking operation may be detected by detecting a moment at which the accelerator pedal of the vehicle is released, or by detecting that the relative-position quantity has reached a predetermined value. The moment at which the vehicle operator feels it necessary to initiate the braking operation may also be detected by detecting a sudden increase of the tension or strain of the vehicle operator. For instance, the moment at which the vehicle operator feels a necessity of rapid or large brake application to the vehicle may be detected by detecting a moment at which the force of gripping of the steering wheel of the vehicle by the operator has increased to a predetermined upper limit, a moment at which the pressure acting on the operator""s seat has increased to a predetermined upper limit, or a moment at which the operator""s heart pulse rate has reached a predetermined upper limit.
The relative-position quantity may be a quantity at a moment of the actual initiation of the braking operation, a quantity at a moment at which the operator feels it necessary to initiate the braking operation, or a quantity determined by those two quantities.
(7) A warning apparatus according to any one of the above modes (1)-(6), further comprising a characteristic-value setting portion manually operable by the operator to set at least one of the above-indicated at least two of the plurality of brake operating characteristic values in the above mode (1), and the threshold-value determining portion is operable to obtain the estimated braking state of the vehicle on the basis of the above-indicated at least one brake operating characteristic value set by the characteristic-value setting portion and the above-indicated at least one characteristic-value relationship stored in the characteristic-value storage portion, the threshold-value determining portion determining the threshold value of the distance on the basis of the estimated braking state obtained.
For instance, one of the two brake operating characteristic values of one of the at least one characteristic-value relationship is set by the manually operable characteristic-value setting portion. In this case, the warning apparatus permits generation of a warning signal at a timing that suits the specific vehicle operator who has set the specific characteristic value.
Where the characteristic value that is set by the characteristic-value setting portion is a value which is influenced by the mental factors and locomotive capacity of the vehicle operator, the timing at which the warning apparatus can be activated to generate the warning signal is further optimized in accordance with the specific metal factors and locomotive capacity of the specific operator. The desired-safety-margin quantity described above with respect to the above mode (4) and the promptness quantity described above with respect to the above mode (5) may be used as values suitably set by the operator with the characteristic-value setting portion. While these quantities change with different vehicle operators, they may also change depending upon the mental states and/or physical conditions of the same operator.
(8) A warning apparatus according to any one of the above modes (1)-(7), further comprising:
a friction-coefficient obtaining portion operable to obtain a friction coefficient of a roadway surface on which the vehicle is running; and
a characteristic-value-relationship determining portion operable to determine the above-indicated at least one characteristic-value relationship on the basis of the friction coefficient obtained by the friction-coefficient obtaining portion.
In the warning apparatus according to the above mode (8), each characteristic-value relationship is determined on the basis of the friction coefficient of the roadway surface. For instance, the characteristic-value storage portion may store a plurality of characteristic-value relationships corresponding to respective different values of the friction coefficient of the roadway surface, and the characteristic-value-relationship determining portion selects one of those stored characteristic-value relationships which corresponds to the friction coefficient value obtained by the friction-coefficient obtaining portion. Alternatively, the characteristic-value-relationship determining portion is arranged to determine the characteristic-value relationship depending upon the obtained friction coefficient value. Further alternatively, the characteristic-value storage portion stores a nominal characteristic-value relationship corresponding to a reference value of the friction coefficient of the roadway surface (e.g., the friction coefficient value of a dry asphalt roadway surface), and the characteristic-value-relationship determining portion is arranged to change this nominal characteristic-value relationship depending upon an amount of deviation of the obtained actual friction coefficient value from the reference value.
As described above, the deceleration value of the vehicle has a close relationship with the actual friction coefficient of the roadway surface, and the desired safety margin (mental state) of the vehicle operator is also influenced by the friction coefficient. For instance, the tension of the vehicle operator is higher when the friction coefficient of the roadway surface is relatively low than when it is relatively high. Accordingly, the time duration between the moment at which the vehicle operator feels it necessary to initiate the braking operation and the moment at which the braking operation is actually initiated tends to be shorter when the friction coefficient is relatively low. In this respect, it is desirable to determine the characteristic-value relationship depending upon the friction coefficient of the roadway surface.
Where a wheel of the vehicle is provided with a friction brake for braking the wheel by forcing a friction member onto a rotor rotating with the wheel, the friction coefficient of the roadway surface may be obtained on the basis of a state of change of the rotating speed of the wheel while the friction member is held forced onto the rotor with a predetermined pressing force for a predetermined time. When the friction coefficient is sufficiently high, the deceleration value of the vehicle corresponds to the pressing force. When the friction coefficient is relatively low, the vehicle deceleration value may be lower than a value corresponding to the pressing force. In this latter case, the vehicle deceleration value cannot exceed a value corresponding to the friction coefficient. Thus, the vehicle deceleration value may not be increased to a value corresponding to the wheel braking force when the friction coefficient is relatively low.
(9) A warning apparatus according to any one of the above modes (1)-(8), further comprising:
a running-environment obtaining portion operable to obtain a running environment of the vehicle; and
a characteristic-value-relationship determining portion operable to determine the above-indicated at least one characteristic-value relationship on the basis of the running environment obtained by the running-environment obtaining portion.
In the warning apparatus according to the above mode (9), each characteristic-value relationship is determined on the basis of the running environment of the vehicle. The running environment includes: a condition of the roadway surface; a kind of the roadway; and environmental conditions such as the weather condition. The condition of the roadway surface includes the friction coefficient and the roughness or bumpiness of the surface. The kind of the roadway includes its running speed limit, and whether the roadway is an express way or an ordinary roadway. The environmental conditions include a fine weather, a rainy weather, a snow fall, and a fog. The running environment of the vehicle described above has a considerable influence on the metal states of the vehicle operator. In this respect, it is desirable to determine the characteristic-value relationship on the basis of the running environment of the vehicle.
(10) A warning apparatus according to any one of the above modes (1)-(9), further comprising:
a running-state obtaining portion operable to obtain the running state of the vehicle; and
a characteristic-value-relationship determining portion operable to determine the above-indicated at least one characteristic-value relationship on the basis of the running state obtained by the running-state obtaining portion.
In the warning apparatus according to the above mode (10), each characteristic-value relationship is determined on the basis of the running state of the vehicle. The running state includes: a state in which the drive wheels of the vehicle are driven; a state in which the vehicle is braked; a state in which the vehicle is turning; and a state in which the running condition is controlled. The running state may be represented by the operating states of the accelerator pedal, the brake operating member (brake pedal) and the steering wheel, and operating states of various switches provided to establish respective running modes of the vehicle.
For example, the braking-delay time described above with respect to the above mode (6) is relatively long while the vehicle drive wheels are driven or the vehicle is turning, and is relatively short while the vehicle is braked. On the other hand, the distance between the vehicle and the front object, at which the vehicle operator feels it necessary to increase the braking force, is relatively short while the vehicle is braked, since the vehicle operator operating the brake operating member is likely to feel that the distance is long enough to assure safety of running of the vehicle. Where the vehicle is running in a running mode so as to maintain a predetermined relative position between the vehicle and the front object, the vehicle operator is generally relaxed, so that the braking-delay time is accordingly increased. Thus, it is desirable to determine the characteristic-value relationship on the basis of the running state of the vehicle.
The warning apparatus according to the above mode (8), (9) or (10) is arranged to determine each characteristic-value relationship on the basis of the friction coefficient of the roadway surface, the running environment or state of the vehicle. However, the threshold-value determining portion may be arranged to determine the threshold value of the distance between the vehicle and the front object, on the basis of the friction coefficient, or the running environment or state of the vehicle. That is, the threshold value is increased or reduced depending upon a change of the friction coefficient or the running environment or state of the vehicle.
(11) A warning apparatus according to any one of the above modes (1)-(10), wherein the vehicle has a controlled running mode in which the running state is controlled on the basis of a relative-position quantity elating to a relative position between the vehicle and the object, and the threshold-value determining portion determines the threshold value of the distance such that the determined threshold value is larger when the vehicle is running in the controlled running mode, than when the vehicle is not running in the controlled running mode.
In the controlled running mode in which the running state of the vehicle is controlled on the basis of the relative-position quantity, the vehicle operator tends to be relaxed, and careless. In view of this tendency, it is desirable to determine the threshold distance to be comparatively long in the controlled running mode.
The threshold value of the distance may be determined on the basis of the running state or environment of the vehicle described above. The threshold value is desirably determined to be comparatively long when the drive wheels are driven, and to be comparatively short when the vehicle is braked. In this respect, it is noted that the braking-delay time tends to be long when the drive wheels are driven with the accelerator pedal being depressed, and that the necessity of generating the warning signal is relatively low during braking of the vehicle. The warning signal if generated during braking of the vehicle is usually annoying to the vehicle operator. Further, it is desirable to determine the threshold value to be larger when it is raining, snowing or foggy, than when it is fine, or when the friction coefficient of the roadway surface is lower than a predetermined threshold than when the friction coefficient is not lower than the threshold.
Alternatively, the threshold value of the distance may be determined on the basis of the moving state of the front object. For instance, the threshold value is determined to be relatively large when the acceleration value of the object is extremely low (when the deceleration value is extremely high).
(12) A warning apparatus according to any one of the above modes (1)-(11), further comprising a safety detecting portion operable to determine whether a positional relationship between the vehicle and the object falls within a predetermined safe region, and the threshold-value determining portion determines the threshold value of the distance when the safety detecting portion determines that the positional relationship does not fall within the safe region.
When the positional relationship between the vehicle and the object is within the safe region, it is not necessary to generate the warning signal, and is therefore not necessary to determine the threshold value of the distance between the vehicle and the object. A determination as to whether the positional relationship is within the safe region may be made by determining whether at least one of the running speed and acceleration value of the vehicle, the moving speed and acceleration of the front object, and the free running time of the vehicle satisfies a predetermined condition of safety.
In the warning apparatus wherein the threshold value of the distance is determined when the positional relationship between the vehicle and the front object is not within the predetermined safe region, a condition in which the positional relationship is not within the safe region may be considered to a condition in which a pre-warning condition to determine whether the distance is shorter than the threshold value is satisfied. When this pre-warning condition is satisfied, there is a relatively high possibility that the distance between the vehicle and the front object will become shorter than the predetermined threshold value, that is, there is a relatively high possibility that the warning signal should be generated. The pre-warning condition may be considered to be a condition in which it is required to determine whether the warning signal should be generated.
(13) A warning apparatus according to any one of the above modes (1)-(12), further comprising a running control portion operable to control the running state of the vehicle on the basis of a relative-position quantity relating to a relative position between the vehicle and the object.
The warning apparatus according to the above mode (13) is capable of controlling the running state of the vehicle on the basis of the relative-position quantity, for instance, such that the positional relationship between the vehicle and the front object coincides with a predetermined relationship. In this case, the warning apparatus may be arranged to generate the waning signal while the running state of the vehicle is controlled by the running control portion, or while the running state is not controlled.
(14) A warning apparatus for an automotive vehicle, operable to generate a warning signal when a distance between the vehicle and an object existing in front of the vehicle is shorter than a predetermined threshold value, characterized by comprising a threshold-value determining portion operable to determine the threshold value of said distance, on the basis of at least one of:
(a) an estimated braking-delay time which is an estimated time duration between a moment at which an operator of the vehicle feels it necessary to initiate a braking operation to brake the vehicle and a moment at which the braking operation is actually initiated;
(b) an estimated vehicle deceleration value which is an estimated value of deceleration of the vehicle as a result of the raking operation by the operator;
(c) a critical-relative-position quantity relating to a relative position between the vehicle and the object at which the operator feels it necessary to initiate the braking operation; and
(d) a moving-state quantity indicative of a moving sate of the object.
In the warning apparatus according to the above mode (14), the threshold value of the distance used to determine whether the warning signal should be generated is determined on the basis of at least one of the estimated-braking-delay time, the estimated vehicle deceleration value of the vehicle, the critical-relative-position quantity and the moving-state quantity indicative of the moving state of the object. The vehicle operator may manually set at least one of the estimated braking-delay time, estimated deceleration value of the vehicle and critical-relative-position quantity. Alternatively, at least one of those three parameters may be determined on the basis of the past operating conditions of the vehicle, or may be a predetermined value.
The technical features according to any one of the above modes (1)-(13) is applicable to the warning apparatus according to the above mode (14).
(15) A warning apparatus for an automotive vehicle, operable to generate a warning signal when a relative-position quantity relating to a relative position between the vehicle and an object in front of the vehicle is on a predetermined one side of a predetermined threshold value on which a distance between the vehicle and the object is shorter than on the other side, characterized by comprising:
a characteristic-value storage portion which stores at least one characteristic-value relationship between at least two of a plurality of brake operating characteristic values relating to a braking operation by an operator of the vehicle to brake the vehicle; and
a threshold-value determining portion operable to determine the threshold value of the relative-position quantity on the basis of at least one of: an estimated braking state of the vehicle estimated on the basis of the above-indicated at least one characteristic-value relationship stored in the characteristic-value storage portion; and a moving-state quantity indicative of a moving state of the object.
The relative-position quantity may be a distance between the vehicle and the front object, or the distance divided by the relative speed of the vehicle and the object. The technical feature according to any one of the above modes (1)-(14) is applicable to the warning apparatus according to the above mode (15).
(16) A warning apparatus for an automotive vehicle, operable to generate a warning signal when a distance between the vehicle and an object existing in front of the vehicle is shorter than a predetermined threshold value, characterized by comprising a threshold-value determining portion operable to determine the threshold value of the distance on the basis of at least one of (a) a running state of the vehicle and (b) a running environment of the vehicle, and at least one of (i) a running-state quantity indicative of the running state of the vehicle and (ii) a moving-state quantity indicative of a moving state of the object.
The technical features according to any one of the above modes (1)-(15) is applicable to the warning apparatus according to the above mode (16).